Access time is total time it takes a computer to request data, and then that request to be met. A good analogy is the time between you ordering a pizza and it being delivered. Access time pertains to devices such as memory, hard drive, CD-ROM (compact disc read-only memory) or other mechanisms. Computer access time is commonly measured in nanoseconds or milliseconds and the lower the time the, better or faster the computer should perform.
Memory access time
With computer memory, access time is the time it takes the computer processor to read data from the memory. When looking at the access time of memory it may be represented in either ns (nanoseconds), MHz, or GHz.